<template>
  <div class="type-nav">
    <div class="container" @mouseenter="showAll"  @mouseleave="leaveIndex">
      <h2 class="all">全部商品分类</h2>
      <nav class="nav">
        <a href="###">服装城</a>
        <a href="###">美妆馆</a>
        <a href="###">尚品汇超市</a>
        <a href="###">全球购</a>
        <a href="###">闪购</a>
        <a href="###">团购</a>
        <a href="###">有趣</a>
        <a href="###">秒杀</a>
      </nav>
      <transition name="sort">
        <div class="sort" v-show="isshow" @mouseleave="leaveIndex"> 
        <!-- //绑定单击事件实现事件委托 -->
        <div class="all-sort-list2" @click="goSearch" >
          <div class="item" v-for="(c1,index) in categoryList" :key="c1.categoryId">
<!--            鼠标移入添加类，鼠标取消类-->
            <h3 @mouseenter="changeIndex(index)"  :class="index === currentIndex?'cur':''">
              <!-- 一级分类 -->
              <a :data-categoryName='c1.categoryName' :data-category1Id='c1.categoryId'>{{c1.categoryName}}</a>
            </h3>
            <!-- 二级分类 -->
            <div class="item-list clearfix" :style="{display:currentIndex == index ?'block':'none'}">
              <div class="subitem" v-for="c2 in c1.categoryChild" :key="c2.categoryId">
                <dl class="fore">
                  <dt>
                    <a :data-categoryName='c2.categoryName' :data-category2Id='c2.categoryId'>{{c2.categoryName}}</a>
                  </dt>
                  <dd>
                    <em v-for="c3 in c2.categoryChild" :key="c3.categoryId">
                     <!-- 三级分类 -->
                      <a :data-categoryName='c3.categoryName' :data-category3Id='c3.categoryId'>{{c3.categoryName}}</a>
                    </em>
                    
                  </dd>
                </dl>
              </div>
            </div>
          </div>
          
        </div>
      </div>
      </transition>
    </div>
  </div>
</template>

<script>
//引入lodash的节流函数
import throttle from 'lodash/throttle'



export default {
  name: 'TypeNav',
  data(){
    return{
      currentIndex:-1,
      isshow:false
    }
  },
  methods:{
    showAll(){
      
      this.isshow = true
    },
    //利用事件委托监听a标签
    goSearch(e){
      //最好的解决方案：编程式导航+事件委托
      //存在一些问题：事件委派，是全部的子节点【h3，dt，dl，em】的事件委派给父亲节点
      //点击a标签的时候，才会进行路由跳转【怎么才能确定单击的是a标签】 
      //存在另一个问题，即使你能确定点击的是a标签，如何区分一级、二级、三级分类的标签
      //第一个问题就是 给a标签添加自定义属性 data-categoryName，区域子节点是没有的
      //事件对象的target属性可以获取到单击的是什么标签
      let element = e.target
      //如果单击的是a标签，那么 a标签一定携带了categoryname属性
      //标签有一个属性  dataset属性可以获取自定义属性与属性值
      let {categoryname,category1id,category2id,category3id} = element.dataset
      
      if(categoryname){
        let location = {name:'search'}
        let query = {categoryName:categoryname}
        if(category1id){
          query.category1Id = category1id
        } else if(category2id){
          query.category2Id = category2id
        } else{
          query.category3Id = category3id
        }
        if(this.$route.params){
          location.query = query
          location.params = this.$route.params
        this.$router.push(location)
        }else {
          location.query = query
          this.$router.push(location)
        }
        
      }
},
    //使用节流，鼠标停留的时间足够50毫秒在执行函数体
    changeIndex:throttle(function(index){
      
      this.currentIndex = index
    },50)
    ,
    leaveIndex(){
      this.currentIndex = -1
      if(this.$route.path != '/home' ){
        this.isshow = false
      }
    }
  },
  mounted() {
   
   
    if(this.$route.path ===  '/home'){
      this.isshow = true
    }

  },
  computed: {
    categoryList() {
      //可是输出查看$store的数据结构来获取数据
      return this.$store.state.home.categoryList
    },
  },
}
</script>

<style lang="less" scoped>
.type-nav {
  border-bottom: 2px solid #e1251b;

  .container {
    width: 1200px;
    margin: 0 auto;
    display: flex;
    position: relative;

    .all {
      width: 210px;
      height: 45px;
      background-color: #e1251b;
      line-height: 45px;
      text-align: center;
      color: #fff;
      font-size: 14px;
      font-weight: bold;
    }

    .nav {
      a {
        height: 45px;
        margin: 0 22px;
        line-height: 45px;
        font-size: 16px;
        color: #333;
      }
    }

    .sort {
      position: absolute;
      left: 0;
      top: 45px;
      width: 210px;
      height: 461px;
      position: absolute;
      background: #fafafa;
      z-index: 999;

      .all-sort-list2 {
        .item {
          h3 {
            line-height: 30px;
            font-size: 14px;
            font-weight: 400;
            overflow: hidden;
            padding: 0 20px;
            margin: 0;

            a {
              color: #333;
            }
          }

          .item-list {
            display: none;
            position: absolute;
            width: 734px;
            min-height: 460px;
            background: #f7f7f7;
            left: 210px;
            border: 1px solid #ddd;
            top: 0;
            z-index: 9999 !important;

            .subitem {
              float: left;
              width: 650px;
              padding: 0 4px 0 8px;

              dl {
                border-top: 1px solid #eee;
                padding: 6px 0;
                overflow: hidden;
                zoom: 1;

                &.fore {
                  border-top: 0;
                }

                dt {
                  float: left;
                  width: 54px;
                  line-height: 22px;
                  text-align: right;
                  padding: 3px 6px 0 0;
                  font-weight: 700;
                }

                dd {
                  float: left;
                  width: 415px;
                  padding: 3px 0 0;
                  overflow: hidden;

                  em {
                    float: left;
                    height: 14px;
                    line-height: 14px;
                    padding: 0 8px;
                    margin-top: 5px;
                    border-left: 1px solid #ccc;
                  }
                }
              }
            }
          }

          &:hover {
            .item-list {
              display: block;
            }
          }
        }
        .cur{
          background: skyblue;
        }
      }
    }
    .sort-enter{
      height: 0px;
    }
    .sort-enter-to{
      height: 461px;
    }
    .sort-enter-active{
      transition: all linear .5s;
    }
  }
}
</style>
